Denise Wilson, the passenger in the car who captured the moment, told People that she noticed a man, Corey Simmons, across from her was holding a pile of math worksheets on his lap. A few stops later, another man sat down next to him and took notice of what Simmons was working on.

Simmons explained to the man, who has not been identified, that his son had recently failed a math test at school, and he was trying to relearn fractions in order to be able to help his son with his homework. The stranger told Simmons he used to be a math teacher and told him to ask him if he had any questions. Wilson said the man then scooted over and started working through the problems one-by-one with Simmons.

"When I saw that, my heart filled up with so much warmth," Wilson said. "Dads don't get enough credit sometimes, I feel like. And come to find out, Corey is a single father. That's amazing to me."

Before the man got off the subway some stops later, Wilson snapped a photo of the two of them and posted it on Facebook where it has since been shared over 40,000 times. Simmons told CBS2 that before that moment, it had been decades since he had solved a fraction problem, but the interaction has helped him better understand them and be better able to help his son.

"It doesn't matter if you fail, it's what you do after you fail," Simmons. "You need help sometimes and you shouldn't want to bite your tongue, to not ask for the help. So don't feel shy to ask someone for help, it's OK."